Field of the Invention
The present invention relates to a fuel cell resin frame equipped membrane electrode assembly including a stepped MEA and a resin frame member. The MEA includes a first electrode, a second electrode, and a solid polymer electrolyte membrane interposed between the first electrode and the second electrode. The resin frame member is provided around an outer circumference of the MEA.
Description of the Related Art
In general, a solid polymer electrolyte fuel cell employs a solid polymer electrolyte membrane. The solid polymer electrolyte membrane is a solid polymer ion exchange membrane. The fuel cell includes a membrane electrode assembly (MEA) where an anode and a cathode are provided respectively on both sides of the solid polymer electrolyte membrane. Each of the anode and the cathode includes a catalyst layer (electrode catalyst layer) and a gas diffusion layer (porous carbon). In the fuel cell, the membrane electrode assembly is sandwiched between separators (bipolar plates). In use, a predetermined number of fuel cells are stacked together to form a fuel cell stack. For example, the fuel cell stack is mounted in a fuel cell electric vehicle as an in-vehicle fuel cell stack.
In some cases, the membrane electrode assembly has structure where components of the MEA (stepped MEA) have different sizes, i.e., the planar size of one of the gas diffusion layers is smaller than the planar size of the solid polymer electrolyte membrane, and the planar size of the other of the gas diffusion layers is the same as the planar size of the solid polymer electrolyte membrane. In this regard, in order to reduce the amount of relatively expensive material used for the solid polymer electrolyte membrane, and protect the thin solid polymer electrolyte membrane having insufficient strength, for example, a frame equipped MEA including a resin frame member has been adopted as a protection member.
As this type of frame equipped MEA, for example, a membrane electrode assembly disclosed in Japanese Laid-Open Patent Publication No. 2007-066766 is known. As shown in FIG. 7, the membrane electrode assembly includes a membrane 1, an anode catalyst layer 2a provided on one side of the membrane 1, and a cathode catalyst layer 3a provided on the other side of the membrane 1. A GDL (gas diffusion layer) 2b and a GDL 3b are provided on both surfaces of the membrane 1, respectively. The planar size of the GDL 2b on the anode side is larger than the planar size of the GDL 3b on the cathode side.
A gasket structural body 4 is provided in an edge area of the MEA. The gasket structural body 4 is formed by combining gasket layers on the cathode side and the anode side positioned at least in part of an area around the ends of the anode catalyst layer 2a and the cathode catalyst layer 3a (preferably, positioned over the entire area around the ends of the anode catalyst layer 2a and the cathode catalyst layer 3a). At least the outer portion of the membrane 1 on the side (GDL 3b side) where the GDL surface area is smaller is joined to the gasket structural body 4 through an adhesive layer 5.